Tubular laminate and process for producing the same

ABSTRACT

A process for producing a tubular laminate which comprises, discharge-treating an outer surface of a tubular fluorine-containing resin molded article in an inert gas atmosphere containing an organic compound having a functional group, extruding a molten resin onto the treated surface and coating the treated surface with the molten resin. According to this process, there can be obtained a strong adhesion between the fluorine-containing resin molded article and the coating resin without using an adhesive. Therefore, an applying step of the adhesive can be omitted and the tubular laminate can be produced continuously.

TECHNICAL FIELD

The present invention relates to a tubular laminate of afluorine-containing resin a process for producing the same.

BACKGROUND ART

A fluorine-containing resin has excellent characteristics such asnon-stickiness, stain resistance, heat resistance, chemical resistance,clearness, ultraviolet ray aging resistance, weatherability, and waterand oil repelling property, which are not possessed by the other resins.However, the fluorine-containing resin is very difficult to be laminatedon the other materials due to its non-sticking characteristic.Therefore, the fluorine-containing resin is not actually widely used inspite of the above-mentioned excellent characteristics. A tubularlaminate is not an exception.

Effort to conduct lamination on a fluorine-containing resin moldedarticle has been first directed to modification of a surface of thefluorine-containing resin molded article, and various modificationmethods have been developed. For example, there are known methods inwhich an electric discharge treatment such as corona discharge isconducted (JP-B-17485/1962, JP-B-51421/1984, JP-B-54848/1990,JP-A-214620/1984, JP-A-9533/1988, JP-A-218336/1988, JP-A-222838/1988), amethod in which a flame treatment or a metallic sodium treatment isconducted (JP-B-10176/1988), a method in which surface roughingtreatment is conducted by sand blast, and the like. In most cases,however, sufficient adhesion may not be obtained only by modifying thesurface of the fluorine-containing resin. Therefore, an adhesive is usedfor lamination.

These methods are similarly applied to lamination of a tubularfluorine-containing resin molded article. JP-B-51421/1984 discloses aprocess for producing a tubular laminate in which after treating anouter surface of an inner layer of the fluorine-containing resin moldedarticle by corona discharge, a rubber-based primer layer is formed onthe treated surface, and an unvulcanized rubber sheet is wrapped on theprimer layer, then vulcanization is conducted.

For forming the primer layer or the adhesive layer, however, more stepsare necessary corresponding thereto. Further, various considerations arerequired for selection of the adhesive.

The present invention provides a process for producing a tubularfluorine-containing resin laminate without an adhesive layer (a primerlayer) and having a strong adhesion to each other.

DISCLOSURE OF THE INVENTION

The present invention relates to a process for producing a tubularlaminate which comprises, discharge-treating an outer surface of atubular fluorine-containing resin molded article in an inert gasatmosphere containing an organic compound having a functional group,extruding a molten resin onto the treated surface, and coating thetreated surface with the molten resin.

The preferred embodiments of the present invention are explainedhereinbelow:

The fluorine-containing resin used in the present invention is notrestricted, provided that a tubular molded article can be produced fromthe resin. Examples are polytetrafluoroethylene (PTFE) or a modifiedcompound thereof, tetrafluoroethylene-perfluoroalkyl vinyl ethercopolymer (PFA), tetrafluoroethylene-hexafluoro-propylene copolymer(FEP), tetrafluoroethylene-ethylene copolymer (ETFE),tetrafluoroethylene-vinylidene fluoride copolymer (TFE/VdF),tetrafluoroethylene-hexafluoro-propylene-perfluoroalkyl vinyl ethercopolymer (EPA), polychlorotrifluoroethylene (PCTFE),chlorotrifluoro-ethylene-ethylene copolymer (ECTFE),chlorotrifluoro-ethylene-vinylidene fluoride copolymer (CTFE/VdF),poly(vinylidene fluoride) (PVdF), poly(vinyl fluoride) (PVF), and thelike. Among them, PTFE, PFA, FEP, ETFE, PCTFE and PVdF are particularlypreferable. The fluorine-containing resin molded article may be either atubular article itself or a coated layer formed on other tubularsubstrates, for example, a metallic pipe made of steel, copper,aluminium or the like, a nonmetallic pipe made of glass, cement, resinor the like.

For the surface modification of the fluorine-containing resin moldedarticle, there are adopted discharge treatments such as corona dischargetreatment, glow discharge treatment, plasma discharge treatment andsputtering treatment (JP-B-17485/1962, JP-B-12900/1974, U.S. Pat. No.3296011). For example, in the corona discharge treatment, the surfacetreatment is carried out by exposing a surface to be modified to anatmosphere of an inert gas (for example, nitrogen gas, helium gas, argongas, or the like) containing an organic compound having a functionalgroup, applying a high frequency voltage between electrodes to generatecorona discharge, thereby producing active species on the surface,subsequentry introducing the functional group of the organic compound orgraft-polymerizing a polymerizable organic compound. Conditions of thecorona discharge may be properly selected according to a dielectricconstant of the fluorine-containing resin molded article.

The feature of the present invention is that the organic compound havinga functional group exists in the atmosphere on the discharge-treatment.The surface of the fluorine-containing resin modified by the dischargetreatment has an increased surface activity, and an extremely enhancedreactivity. A surface tension after the modification is preferably notless than approximately 30 dyn/cm, particularly not less thanapproximately 40 dyn/cm.

Examples of the functional group are, for instance, hydroxyl group,epoxy group, carboxyl group, ester group, carbonyl group, isocyanategroup, nitrile group, amino group, ether bond, polymerizable doublebond, and the like. However, the functional group is not restricted tothem. The compound having the functional group may be either apolymerizable compound or a non-polymerizable compound. Non-restrictedexamples are listed below.

(a) Compounds having hydroxyl group

Polymerizable organic compounds:

Polyhydric alcohols such as ethylene glycol and gricerol; and the like.

Non-polymerizable organic compounds:

Monohydric alcohols such as methanol, ethanol and phenol; and the like.

(b) Compounds having epoxy group

Polymerizable organic compounds:

Epoxydized compounds such as glycidyl methacrylate and epichlorohydrin;and the like.

Non-polymerizable organic compounds:

Glycidyl ethers, epoxy alkanes; and the like.

(c) Compounds having carboxyl group

Polymerizable organic compounds:

Dicarboxylic acids such as phtalic acid and maleic acid; acrylic acidssuch as acrylic acid and methacrylic acid; and the like.

Non-polymerizable organic compounds:

Carboxylic acids such as formic acid and acetic acid; and the like.

(d) Compounds having ester group

Polymerizable organic compounds:

Esters such as methyl acrylate, methyl methacrylate, ethyl acrylate,glycidyl methacrylate and diallyl phthalate; and the like.

Non-polymerizable organic compounds:

Esters such as ethyl formate and ethyl acetate; and the like.

(e) Compounds having carbonyl group

Polymerizable organic compounds:

The carbonyl group in the carboxylic acids or the esters of (c) and (d).

Non-polymerizable organic compounds:

Ketones such as acetone (carbonyl group in monofunctional carboxylicacids and esters).

(f) Compounds having isocyanate group

Isocyanates such as tolylenediisocyanate and its derivatives.

(g) Compounds having nitrile group

Polymerizable organic compounds:

Acrylonitriles such as acrylonitrile and methacrylonitrile;cyanoacrylates; and the like.

Non-polymerizable organic compounds:

Nitriles such as acetonitrile and propionitrile; and the like.

(h) Compounds having amino group

Polymerizable organic compounds:

Melamines; diamines; acrylamides; and the like.

Non-polymerizable organic compounds:

Various amines and ammonium salts; and the like.

(i) Compounds having ether bond

Polymerizable organic compounds:

Vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; and thelike.

Non-polymerizable organic compounds:

Various ethers such as diethyl ether and glycidyl methyl ether; or thelike.

(j) Compounds having polymerizable double bond

Olefines such as ethylene and propylene; vinyl carboxylates such asvinyl acetate; perhalogenated olefins such as chlorotrifluoroethylene,tetrafluoroethylene and hexafluoropropylene; or the like.

The organic compound is required to be present in gaseous (steam) statein the inert gas atmosphere. The concentration varies with kinds of theorganic compound, and is usually 0.1 to 10.0% by mole, preferably 0.5 to7.0% by mole. Therefore, the organic compound necessarily has a vaporpressure of at least not less than 1 mmHg at the discharge treatmenttemperature (usually from 20° to 100° C.). In case of the polymerizableorganic compound, it is particularly preferable to combine with acoating resin comprising a polymer obtained by polymerization orcopolymerization of the polymerizable organic compound. In case of thenon-polymerizable organic compound, it is required to have at least oneactive hydrogen or to be a compound having a bond dissociation energy ofnot more than 100 kcal, since the non-polymerizable organic compound hasto be activated by the discharge treatment.

In the present invention, the coating layer is formed by melt-extrudingthe coating resin directly on the thus surface-modified tubularfluorine-containing resin molded article. The preferable coating resinhas a lower melting temperature than that of the fluorine-containingresin of the inner resin, an excellent wettability with the surfacetreated fluorine-containing resin molded article, and a surface tensionof not less than 30 dyn/cm. When the surface tension is less than that,since the wettability is worse, adhesion is not good.

The preferable coating resins are, for example, polyamides such as nylon12, nylon 11, nylon 6 and nylon 66; polyolefins such aspolyvinylchloride (PVC); poly(vinyl acetate), poly(methyl methacrylate),polyacrylonitrile, polyethyleneterephthalate, polyurethane, and thelike. Among them, particularly preferable is a polymer obtained bypolymerization or copolymerization of a monomer which has the samefunctional group as or a functional group having an affinity with thefunctional group of the organic compound present in the atmosphere formodification, because the polymer has an improved adhesion. A polymerwhich has a good excellent wettability with the modified surfaceprovides a sufficient adhesion.

Into the coating resin, there may be blended usual additives, forexample, curing agents, ultraviolet ray absorbents, fillers, pigments,antistatic agents, plasticizers, and the like.

As an extrusion-coating method, there may be employed a method similarto a usual electric cable coating method. For example, there is a methodwhich comprises, discharge-treating an outer surface of a tubularfluorine-containing resin molded article laminated on a mandrel made ofresin or metal in an inert gas atmosphere which contains the organiccompound having a functional group, subsequently extruding a coatingresin continuously through a crosshead of an extruder, and then coatingthe outer surface with the resin. The extrusion-coating method is notlimited to this method.

According to the present invention, there can be continuously produced atubular laminate made of different kinds of resins with strong adhesiontherebetween without using an adhesive.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is explained by means of the following Examples.The present invention is not limited only to the Examples.

EXAMPLE 1

A tubular molded article (outer diameter 6.0 mm.o slashed., thickness0.2 mm) made of ETFE (melting temperature 260° C.) was discharge-treatedin a nitrogen gas atmosphere containing 7% by mole of vinyl acetatevapor under a charge density of 3 W/cm² to obtain a tubular moldedarticle of which outer surface was modified with vinyl acetate (surfacetension after modification 45 dyn/cm).

Onto the surface modified tubular fluorine-containing resin moldedarticle was extruded a molten nylon 12 (melting temperature 180° C.,surface tension 36 dyn/cm) heated at 220° C. to form a coating layerhaving a thickness of 1.0 mm.

When peel strength of the resulting laminate was measured according tothe following method, the peel strength was 3.0 kgf/inch. (Peelstrength)

A universal tension meter (Tensiron available from Orientech KabushikiKaisha) was used to carry out 180° peel. Stretching rate was 100 mm/min.

EXAMPLES 2 to 6

Tubular fluorine-containing resin molded articles were discharge-treatedunder the conditions shown in Table 1 according to the method of Example1 to modify their surfaces. The coating resins shown in Table 1 weremelt-extruded to obtain tubular laminates, and the peel strengths weremeasured. The results are shown in Table 1.

Comparative Example 1

A molten resin (nylon 12) is extruded to obtain a tubular laminatecoated herewith in the same manner as in Example 1 except that thesurface treatment was not carried out. The peel strength was not morethan 0.1 kgf/inch.

Comparative Example 2

The surface modification was carried out and a molten resin (nylon 12 )was extruded to obtain a tubular laminate coated therewith in the samemanner as in Example 1 except that the discharge treatment was conductedin the absence of vinyl acetate. The peel strength was 0.5 kgf/inch.

Comparative Example 3

A coating resin Was extruded to obtain a tubular laminate coatedtherewith in the same manner as in Example 1 except that polypropylenewas used instead of nylon 12 as the coating resin. The peel strength was0.2 kgf/inch.

Each abbreviation used in Tables 1 to 3 has the following meaning.

(Fluorine-containing resin)

FEP: Tetrafluoroethylene-hexafluoropropylene copolymer.

ETFE: Tetrafluoroethylene-ethylene copolymer

PFA: Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer

(Organic compound)

VAc: Vinyl acetate

GMA: Glycidyl methacrylate

(Coating resin)

PU: Polyurethane elastomer

PE: Polyethylene

PP: Polypropylene

                                      TABLE 1                                     __________________________________________________________________________                            Surface tension of                                                                    Coating resin                                       Material of tubular                                                                    Discharge-treatment                                                                    molded article                                                                        Kind Surface                                        molded article                                                                         atmosphere                                                                             after modification                                                                    (melting                                                                           tension                                                                            Peel strength                       Example                                                                             (melting point °C.)                                                             (% by mole)                                                                            (dyn/cm)                                                                              point °C.)                                                                  (dyn/cm)                                                                           (kgf/inch)                          __________________________________________________________________________    1     ETFE     N.sub.2 /VAc (7)                                                                       45      Nylon 12                                                                           36   3.0                                       (260)                     (180)                                         2     FEP      The same as above                                                                      43      Nylon 12                                                                           36   2.5                                       (270)                                                                   3     PFA      The same as above                                                                      42      Nylon 12                                                                           36   2.2                                       (310)                                                                   4     ETFE     N.sub.2 /GMA (7)                                                                       47      Nylon 11                                                                           38   3.3                                                                 (190)                                         5     ETFE     N.sub.2 /VAc (7)                                                                       45      PU   39   2.8                                                                 (150)                                         6     ETFE     The same as above                                                                      45      PET  45   3.1                                                                 (235)                                         Comparative                                                                         ETFE     No treatment                                                                           22      Nylon 12                                                                           36   ≦0.1                         Example 1                                                                     Comparative                                                                         ETFE     N.sub.2 alone                                                                          25      Nylon 12                                                                           36   0.5                                 Example 2                                                                     Comparative                                                                         ETFE     N.sub.2 /VAc (7)                                                                       45      PP   29   0.2                                 Example 3                       (160)                                         __________________________________________________________________________

INDUSTRIAL APPLICABILITY

According to the present invention, there can be obtained a strongadhesion between the tubular fluorine-containing resin molded articleand the coating resin without using an adhesive. Therefore, an applyingstep of the adhesive can be omitted as well as the tubular laminate canbe produced continuously.

We claim:
 1. A process for producing a tubular laminate which comprises,discharge-treating an outer surface of a tubular fluorine-containingresin molded article in an inert gas atmosphere containing an organiccompound having a functional group, extruding a molten resin onto thetreated surface, and coating the treated surface with the molten resin,the coating resin having a melting point lower than an inner layer ofthe fluorine-containing resin and a surface tension of not less than 30dyn/cm.
 2. The process of claim 1, wherein the functional group of theorganic compound is hydroxyl group, epoxy group, carboxyl group, estergroup, carbonyl group, isocyanate group, nitrile group, amino group,ether bond or polymerizable double bond.
 3. The process of claim 1,wherein the fluorine-containing resin is polytetrafluoroethylene,tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer,tetrafluoroethylene-hexafluoropropylene copolymer,tetrafluoroethylene-ethylene copolymer, polychlorotrifluoroethylene orpoly (vinylidene fluoride).
 4. A tubular laminate having a resin coatinglayer on a tubular fluorine-containing resin molded article, obtained bydischarge-treating an outer surface of the tubular fluorine-containingresin molded article in an inert gas atmosphere containing an organiccompound having a functional group, extruding a molten resin onto thetreated surface, and coating the treated surface with the molten resin,the coating resin having a melting point lower than an inner layer ofthe fluorine-containing resin and a surface tension of not less than 30dyn/cm.
 5. The tubular laminate of claim 4, wherein the functional groupof the organic compound is hydroxyl group, epoxy group, carboxyl group,ester group, carbonyl group, isocyanate group, nitrile group, aminogroup, ether bond or polymerizable double bond.
 6. The tubular laminateof claim 4, wherein the fluorine-containing resin ispolytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ethercopolymer, tetrafluoroethylene-hexafluoropropylene copolymer,tetrafluoroethylene-ethylene copolymer, polychlorotrifluoroethylene orpoly (vinylidene fluoride).
 7. A tubular laminate comprising a tubularmolded article of a fluorine-containing resin coated with a coatingresin having a melting point lower than the fluorine-containing resinand a surface tension of not less that 30 dyn/cm, the laminate obtainedby discharge-treating an outer surface of the tubular molded article inan inert gas atmosphere containing an organic compound having afunctional group, and extruding the coating resin in a molten state ontothe outer surface.
 8. The tubular laminate of claim 7, wherein thefunctional group of the organic compound is hydroxyl group, epoxy group,carboxyl group, ester group, carbonyl group, isocyanate group, nitrilegroup, amino group, ether bond or polymerizable double bond.
 9. Thetubular laminate of claim 7, wherein the fluorine-containing resin ispolytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ethercopolymer, tetrafluoroethylene-hexafluoropropylene copolymer,tetrafluoroethylene-ethylene copolymer, polychlorotrifluoroethylene orpoly (vinylidene fluoride).
 10. The process of claim 1, wherein theorganic compound having a functional group is a member selected from thegroup consisting of monohydric alcohols, polyhydric alcohols, epoxydizedcompounds, carboxylic acids, dicarboxylic acids, esters, ketones,isocyanates, nitriles, acrylonitriles, melamines, diamines, acrylamides,amines, ammonium salts, vinyl ethers, diethyl ether, glycidyl methylether, and olefins.
 11. The process of claim 1, wherein the organiccompound having a functional group is a member selected from the groupconsisting of ethylene glycol, gricerol, methanol, ethanol, phenol,glycidyl methacrylate, epichlorohydrin, glycidyl ethers, epoxy alkanes,phtalic acid, maleic acid, acrylic acids, methacrylic acids, formicacid, acetic acid, methyl acrylate, methyl methacrylate, ethyl acrylate,glycidyl methacrylate, diallyl phthalate, ethyl formate, ethyl acetate,acetone, tolylenediisocyanate, acrylonitrile, methacrylonitrile,cyanoacrylates, acetonitrile, propionitrile, melamines, diamines,acrylamides, amines, ammonium salts, vinyl methyl ether, and vinyl ethylether, diethyl ether, glycidyl methyl ether, ethylene, propylene, vinylacetate, chlorotrifluoroethylene, tetrafluoroethylene, andhexafluoropropylene.
 12. The process of claim 1, wherein the moltenresin is a member selected from the group consisting of polyamides andpolyolefins.
 13. The process of claim 1, wherein the molten resin isselected from the group consisting of nylon 12, nylon 11, nylon 6, andnylon 66, polyvinyl chloride, poly(vinyl acetate), poly(methylmethacrylate), polyacrylonitrile, polyethyleneterephthalate, andpolyurethane.
 14. The tubular laminate of claim 4, wherein the organiccompound having a functional group is a member selected from the groupconsisting of monohydric alcohols, polyhydric alcohols, epoxydizedcompounds, carboxylic acids, dicarboxylic acids, esters, ketones,isocyanates, nitriles, acrylonitriles, melamines, diamines, acrylamides,amines, ammonium salts, vinyl ethers, diethyl ether, glycidyl methylether, and olefins.
 15. The tubular laminate of claim 4, wherein theorganic compound having a functional group is a member selected from thegroup consisting of ethylene glycol, gricerol, methanol, ethanol,phenol, glycidyl methacrylate, epichlorohydrin, glycidyl ethers, epoxyalkanes, phtalic acid, maleic acid, acrylic acids, methacrylic acids,formic acid, acetic acid, methyl acrylate, methyl methacrylate, ethylacrylate, glycidyl methacrylate, diallyl phthalate, ethyl formate, ethylacetate, acetone, tolylenediisocyanate, acrylonitrile,methacrylonitrile, cyanoacrylates, acetonitrile, propionitrile,melamines, diamines, acrylamides, amines, ammonium salts, vinyl methylether, and vinyl ethyl ether, diethyl ether, glycidyl methyl ether,ethylene, propylene, vinyl acetate, chlorotrifluoroethylene,tetrafluoroethylene, and hexafluoropropylene.
 16. The tubular laminateof claim 4, wherein the molten resin is a member selected from the groupconsisting of polyamides and polyolefins.
 17. The tubular laminate ofclaim 4, wherein the molten resin is selected from the group consistingof nylon 12, nylon 11, nylon 6, and nylon 66, polyvinyl chloride,poly(vinyl acetate), poly(methyl methacrylate), polyacrylonitrile,polyethyleneterephthalate, and polyurethane.
 18. The tubular laminate ofclaim 7, wherein the organic compound having a functional group is amember selected from the group consisting of monohydric alcohols,polyhydric alcohols, epoxydized compounds, carboxylic acids,dicarboxylic acids, esters, ketones, isocyanates, nitriles,acrylonitriles, melamines, diamines, acrylamides, amines, ammoniumsalts, vinyl ethers, diethyl ether, glycidyl methyl ether, and olefins.19. The tubular laminate of claim 7, wherein the organic compound havinga functional group is a member selected from the group consisting ofethylene glycol, gricerol, methanol, ethanol, phenol, glycidylmethacrylate, epichlorohydrin, glycidyl ethers, epoxy alkanes, phtalicacid, maleic acid, acrylic acids, methacrylic acids, formic acid, aceticacid, methyl acrylate, methyl methacrylate, ethyl acrylate, glycidylmethacrylate, diallyl phthalate, ethyl formate, ethyl acetate, acetone,tolylenediisocyanate, acrylonitrile, methacrylonitrile, cyanoacrylates,acetonitrile, propionitrile, melamines, diamines, acrylamides, amines,ammonium salts, vinyl methyl ether, and vinyl ethyl ether, diethylether, glycidyl methyl ether, ethylene, propylene, vinyl acetate,chlorotrifluoroethylene, tetrafluoroethylene, and hexafluoropropylene.20. The tubular laminate of claim 7, wherein the molten resin isselected from the group consisting of nylon 12, nylon 11, nylon 6, andnylon 66, polyvinyl chloride, poly(vinyl acetate), poly(methylmethacrylate), polyacrylonitrile, polyethyleneterephthalate, andpolyurethane.